1. Field of the Invention
The present invention relates to a machining apparatus for use in cutting, grinding or effecting any other machining.
2. Related Arts
Referring to FIG. 9, a dicing apparatus for cutting semiconductor wafers into small square pieces has a spindle unit 24 equipped therewith. The spindle unit 24 has a rotary spindle 22 air-borne in its spindle housing 23 by ejecting air streams from radial bearings 39 and thrust bearings 40 at an increased pressure. Thus, the rotary spindle 22 having a dicing blade 18 fixed to its end is floated in non-contact condition within the spindle housing 23. Even when the rotary spindle 22 is not rotating, the high-pressure air is supplied from a high-pressure air source 43 to the spindle housing 23 via an associated air channel 41. As shown, the rotary spindle 22 is integrally connected to the shaft of a synchronous motor 29a. When the synchronous motor 29a is driven, the rotary spindle 22 and the dicing blade 18 are rotated.
While the dicing blade 18 is rotated at an increased speed, the spindle unit 24 is lowered, and then, water is ejected from a pair of water nozzles 94 toward a semiconductor wafer W, which is carried and moved back and forth by the chuck table 15 of the dicing apparatus, thereby permitting the dicing blade 18 to cut the semiconductor wafer W.
Rotation of the rotary spindle 22 at an increased speed will cause thermal expansion of the rotary spindle 22 and spindle housing 23, thus allowing the dicing blade 18 to be displaced relative to the semiconductor wafer W. The deviation thus caused adversely affects the accuracy of the cutting. Cooling water is supplied to the spindle housing 23 ceaselessly even when the rotary spindle 22 is not rotating, thus cooling the spindle 22 with the result that the dicing blade 18 is prevented from moving apart from the correct position. With recourse to this remedy, however, a lot of cooling water is required uneconomically.
While dicing a semiconductor wafer, cooling water is ejected to the machining area to produce a debris-abundant mist by cutting the semiconductor substance, thus causing some parts of the machining apparatus to be contaminated with the debris when exposed to such mist. To prevent such contamination it is necessary that the debris-abundant mist be purged from the machining area to the outside. The dicing apparatus, however, is installed in the air-cleaning room. Clean air, therefore, is removed from the air-cleaning room all the time. This is uneconomical because air-cleaning costs much.
The rotary spindle 22 needs to be kept in floating condition all the time by applying high-pressure air to the rotary spindle 22 via the radial and thrust bearings 39 and 40. This is uneconomical, too.
Any machining apparatus having a machining tool attached to its rotary spindle other than the dicing apparatus has the same problem as described above.
One object of the present invention is to provide a machining apparatus having a machining tool attached to its spindle, which can save fluids such as water, compressed air and clean air.
To attain this object a machining apparatus comprising: at least means for holding a workpiece to be machined; a spindle unit comprising a rotary spindle having a machining element attached thereto for effecting a required machining work on the workpiece and a spindle housing rotatably bearing said rotary spindle; and means for supplying said spindle unit with fluid for use in machining said workpiece, is improved according to the present invention in that said means for supplying said spindle unit with fluid includes a flow control provided in the fluid flowing passage for controlling the flow rate of said fluid in response to the rotating and stopping of said rotary spindle.
Said means for supplying said spindle unit with fluid may comprise at least a cooling water source, a coolant feeding conduit for feeding said spindle housing with cooling water, and a coolant draining conduit for draining all the cooling water from said spindle housing after use; said coolant feeding conduit having a first control valve as said flow control, thereby reducing or stopping cooling water to said spindle housing when said rotary spindle is not rotating.
Said spindle housing may have a pneumatic bearing for bearing said rotary spindle with high-pressure air, said spindle housing being connected to a high-pressure air supply via an associated air duct.
Said air duct may be equipped with a second control valve as air flow control, which is responsive to non-rotating of said rotary spindle for preventing the high-pressure air from flowing to said spindle housing.
A machining apparatus may further comprise demisting means for drawing and removing the mist from the working area where the machining element confronts the workpiece, allowing machining liquid to sputter in the form of mist, said demisting means including a duct opening at the working area for drawing the mist from the working area, said duct being equipped with a flow control.
Said flow control may comprise a fan and/or a third control valve, which may be made to stop its rotation or may be closed in response to absence of mist.
Other objects and advantages of the present invention will be understood from the following description of a machining apparatus according to one preferred embodiment of the present invention, which is shown in accompanying drawings.